Incandescent lamp manufacture



Dec. 16, 1969 STO ET AL 3,483,609

INCANDESCENT LAMP MANUFACTURE Filed Oct. 31, 1967 15g 26 Fig 2. 24

lm/en tofs: r F1 9 MeLViTW L. S tone {Ll/W az Geov cge K Dan R0 1 Md y nited States Patent US. Cl. 2925.15 3 Claims ABSTRACT OF THE DISCLOSURE In the manufacture of a high wattage compact halogen cycle lamp having a planar or multi-segment filament which requires provision for expansion and contraction of the filament coil segments, the support structure at one end of the filament includes a conventional bridge which carries filament support wires and leads which are pinch sealed in one end of a quartz tube. Spring supports are hung from the loops connecting filament coil segments near the open bottom end of the tube which is then pinch sealed to embed the free ends of the spring supports, and then the seal is stretched while still plastic to preload the spring supports.

BACKGROUND OF THE INVENTION Field of the invention The invention relates generally to electric incandescent lamps and particularly to high wattage lamps. Still more particularly, the invention relates to the manufacture of a high wattage lamp having a multiple segment planar type filament and incorporated in the small compact envelope of a halogen cycle lamp with provision for incorporation of a structure which will permit expansion and contraction of the filament segments when the lamp is turned on and oft".

Description of the prior art In certain incandescent lamp types there is used a so-called planar type filament which is composed of a plurality of helically coiled segments arranged in side-byside relation in or adjacent to a common plane and connected in series by loop or bend portions between adjacent segments at either end of the filament. The filament coil segments are supported by support wires which engage the said loop portions and which are, in turn, usually supported from bridge members which are, in turn, supported from sturdy side rods. It is well known that during intermittent operation of high wattage lamps of, for example, about 1500 watts, 120 volts and higher, unless special constructions are used, the coils will tend to stick to the support wires and become distorted sufficiently to result in early burn outs and/or reduced efficiencies. In conventional type lamps it is relatively easy to provide a sliding or floating bridge which will rise and fall upon coil expansion and contraction. Such a construction, generally used, is shown in Patent 2,677,118 to M. L. Stone.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a halogen regenerative cycle lamp, with its advantages of virtual freedom from blackening and consequent high maintained light output at high efficiency for a long, useful life, and of high wattage incorporating a multi-segment filament with means for permitting expansion and contraction of the filament segments. Attempts to incorporate a conventional floating bridge construction of the type used in conventional planar filament lamps resulted in a cumbersome, difficult and costly structure for incorporation in the necessarily compact envelope of a halogen cycle lamp.

3,483,609 Patented Dec. 16, 1969 "ice In accordance with one aspect of the invention, the aforesaid object is attained by first assembling a multisegment filament mount with its leads sealed in one end of a vitreous envelope having its other end open, and with a spring support wire engaging each bend portion between adjacent segments at the bottom of the filament and extending toward the open lower end of the envelope, and then heating the lower end of the envelope and pinching it to form a seal with the lower end of the spring support wires embedded therein, and stretching the plastic sealed lower end of the envelope sufiiciently to preload the spring support wires.

BRIEF DESCRIPTION OF THE DRAWING In the drawing,

FIG. 1 is an elevation of a lamp made in accordance with the invention;

FIG. 2 is an elevation, partly in section, showing the assembly of filament mount and envelope preparatory to pinch sealing the lead-in conductors in the lower end of the envelope;

FIG. 3 is an elevation similar to FIG. 2 but with the envelope inverted and the spring supports attached to the filament preparatory to pinch sealing said supports in the then lower end of the envelope;

FIG. 4 is an elevation similar to FIG. 3 but at right angles thereto and illustrating the pinching and stretching of the seal at the lower end of the envelope;

FIG. 5 is a fragmentary elevation of a modification of the end of the lamp showing the filament spring supports attached to a bridge member; and

FIGS. 6 to 9 are elevations of modified forms of spring support members.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawing, the lamp shown therein comprises a tubular envelope 1 of vitreous material, preferably essentially fused silica or quartz glass, containing a tungsten wire multi-segment or planar filament 2 composed of a plurality of helically coiled segments 3 arranged in side-by-side relation substantially in a single common plane and having loop or bend portions 4 and 5 connecting the ends of adjacent segments at the top and bottom, respectively, of the filament. The filament terminates in coiled leg portions 6 at the upper ends of the outermost segments 3 and which are secured to the ends of tungsten inner lead wire portions 7 which are welded to molybdenum foils 8 to which are welded outer leads, in this case pairs of outer lead wire portions 9. The foils 8 are hermetically sealed in a flattened pinch seal 10 in which are also embedded adjacent portions of the inner and outer lead wire portions 7 and 9. The upper end of the filament 2 is additionally supported by support wires 11 which have hook portions at their lower ends engaging the loops or bends 4 between adjacent filament segments; and portions of said supports 11, as well as portions of inner leads 7, are embedded in a quartz bridge 12.

In order to permit the filament segments 3 to expand and contract upon heating and cooling when the lamp is energized and de-energized, there are provided spring support members 14 of wire, preferably tungsten, having hook-shaped ends 15 engaging the loops or bends 5 which connect the lower ends of adjacent segments 3 and also having helical coil spring portions 16. The lower ends of the supports 14 are embedded and anchored in a pinch seal 17 at the bottom of the envelope 1, with the spring portions 16 preloaded or stretched while the filament 2 is cold, as fully described hereinafter.

The envelope 1 is filled with an inert gas such as nitrogen, argon, krypton or xenon or mixtures thereof,

preferably at substantial pressure of at least several hundred torr, and also contains a small quantity of a halogen such as iodine or bromine or compounds thereof such as hydrogen bromide or hydrocarbons of bromine which function in known manner as a regenerative getter. The envelope may be evacuated and filled through an exhaust tube, the sealed or tipped-off residue of which is shown at 18.

As shown in FIG. 1, the lamp may also be provided with pairs of auxiliary support wires 19 anchored in the pinch seals 17 for supporting the lamp within an outer bulb in known manner. By way of example only, and to illustrate its compact size, the lamp may be of 2000 watt, 120 volt rating in an envelope 1 of about 1% inch diameter and overall length, including the seals 10 and 17, of about 3 inches.

In the manufacture of the lamp the preassembled filament mount unit consisting, as seen in FIG. 2, of the filament 2, bridge 12, supports 11 and composite lead-in conductors 7, 8, 9, is assembled with the Open ended cylindrical quartz tube or envelope 1. The outer lead wire portions 9 are supported in deep holes or wells 20 in a base or chuck member 21, and the mount is enclosed in the quartz tube 1 which is supported by a suitable holder comprising jaws indicated at 22 in FIG. 4, with the exhaust tube 18 connected to a supply of inert gas such as nitrogen. The lower end of tube 1 is positioned a slight distance from the upper surface of the base member 21, and the filament 2 is temporarily supported approximately in a plane through the axis of tube 1 by pairs of wires or prongs 23 which straddle the filament 2 and which project downward from a cap member 24 which fits snugly on the upper end of the tube 1.

A flow of the inert gas is started through exhaust tube 18 and out the bottom of tube 1 to purge the tube 1 of air and provide a protective atmosphere which prevents oxidation of the metal parts of the mount during the sealing operation. The bottom end of tube 1 is then heated intensely and softened by suitable burners. The burners are preferably directed at the tube 1 normal to the plane of the filament 2, and the force of the burners forms the plastic lower end of the tube to a generally oval r elliptical shape preparatory to pinching that end by suitable pinch jaws illustrated at 25 in FIG. 4. The pinch seal (shown at the top in FIGS. 1 and 3) is thereby formed to close the end of the tube 1 and hermetically seal therein the foil portions 8 of the lead-in conductors. Adjacent portions of the inner and outer leads 7 and 9 are also em bedded in the pinch seal 10 to firmly anchor the filament mount and align the filament 2 in the axis of the tube 1. It may be noted that the pinch jaws are preferably relieved at areas on opposite sides of the location of the foils 8 to provide raised pads or bosses 26, whereby to restrict the lateral fiow of the plastic quartz across the faces of the foils which tends to distort and tear the foils. The quartz flow is still better balanced or controlled by providing additionally relieved areas in the faces of the jaws 24 which form the narrower pads or bosses 27 between the bosses 26.

The tube 1 is then raised to withdraw the leads 9 from the holes 20, and inverted as shown in FIG. 3. The spring supports 14 are then hung from the filament loops 5 by their hook ends 15 and with their lower ends terminating short of the open lower end of the tube 1. The supplemental support wires 19 are also loaded into the holes 20 in base or chuck member 21. The tube is then lowered so that its lower end is spaced only slightly from the base member 21 and, with inert gas flowing through exhaust tube 18 and tube 1, the then lower end of tube 1 (FIG. 3) is softened and pinch sealed by jaws (FIG. 4) in the same manner as before to form the second pinch seal 17 in which the lower ends of wire spring members 14 are firmly embedded, along with the upper ends of support wires 19. The two pinch seals 10 and 17, and the filament 2 are in a common plane which also contains the axis of bulb 1.

Then, while the area of the tube 1 at the seal 17 is still plastic, the spring portions 16 are preloaded by stretching the seal an amount necessary to give the desired spring tension. The stretching of the seal is accomplished by a relative movement apart of the envelope holder jaws 2.2 and the base member 21, preferably by an upward movement of the jaws 22 in which the tubular envelope 1 is firmly held.

The envelope 1 is subsequently evacuated and filled with a desired inert gas and halogen, and the exhaust tube 18 is tipped off. The lamp unit of FIG. 1 may then have a base attached to the pinch seal 10 containing the leadin conductors, or it may be mounted in an outer gas-filled bulb, for example as a replacement for the filament of a lamp such as shown in the aforesaid Patent 2,677,118.

Since the same pair of jaws 25 is used to form both the pinch seals 10 and 17, the seal 17 will also contain the pads or bosses 26 and 27.

The resulting construction is not only made adaptable to lamps of the halogen regenerative cycle type, but it also has advantages over the conventional floating bridge construction of prior art lamps. For example, it is operable in almost any burning position, it is less noisy when operated on a silicon control rectifier dimming circuit, and it makes possible use of a smaller size of the expensive quartz for the lamp envelope.

In FIG. 5 there is shown the lower end of a lamp which is like that shown in FIG. 1 and in which corresponding parts carry the same numerals, except that in the FIG. 5 lamp the spring support members 14 are tied together by a quartz bridge 28 like the bridge 12.

FIGS. 6 to 9 show alternative forms of spring supports in which the preferred cylindrical helical spring 16 of the supports 14 of FIG. 1 is replaced in FIG. 6 by a U-shaped portion 29 of the wire 14b, in FIG. 7 by a circular loop portion 30 of wire 14c, in FIG. 8 by a conical helical spring portion 31 of wire 14d, and in FIG. 9 by a double conical helical spring portion 32 of wire 14c.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In the assembly of an incandescent lamp having a pair of lead-in conductors sealed through an upper end of an envelope of vitreous material having its lower end open and a filament comprising at least a pair of coiled wire segments anchored at their proximate upper ends from said upper end of the envelope and electrically connected to respective said lead-in conductors and extending toward said open lower end of the envelope with their lower distal ends joined by a bend portion, and a support wire member including a spring portion, said support wire member being attached to the said bend portion of the filament and hanging therefrom downwardly toward but terminating short of the open lower end of said envelope, the method which comprises softening the open lower end of said envelope, pinching it to form a seal with the lower end of said support wire embedded therein and terminating wholly therewithin, and maintaining a firm hold on the plastic pinch seal portion and also on a rigid portion of the envelope while effecting a relative movement apart of the said pinch seal portion and the said rigid portion so as to stretch the plastic sealed end of the envelope relative to the remainder thereof with the support wire end caught in the seal so as to stretch and preload the said spring portion of the supportwire.

2. The assembly of a lamp as set forth in claim 1 wherein the filament comprises an even number of coiled segments in excess of two arranged in side-by-side relation adjacent a common plane and connected in series by bend portions and having a support wire member hanging from each bend portion at the lower end of the filament, and wherein the pinching is in a direction to form a flattened seal which is located substantially in the said common plane and in which the ends of said support wires are embedded.

3. The method of assembling an incandescent lamp comprising a filament mount structure including a filament comprising at least a pair of coiled wire segments which extend in generally side-by-side relation and are joined at one end by a bend portion and which have their other ends supported from and electrically connected to a pair of lead in conductors which extend away from said filament in generally parallel spaced alignment, which method comprises enclosing said mount structure in an open ended tubular envelope of vitreous material with the outer ends of said lead-in conductors projecting beyond one end of said envelope, heating said one end of the envelope to a plastic condition and pinching it to form a first pinch seal in which portions of said leadin conductors are hermetically embedded, arranging the envelope in a vertical position with said first pinch seal uppermost and the said bend portion of the filament lowermost, attaching to the said bend portion of the filament a support wire member having an intermediate spring portion and a lower end portion extending downwardly toward but terminating short of the then lower Open end of the envelope, heating the said lower open end of the envelope to a plastic condition and pinching it to form a second pinch seal with the lower end of the support Wire member embedded therein and terminating wholly therewithin, and maintaining a firm hold on the plastic pinch seal portion and also on a rigid portion of the envelope while effecting a relative movement apart of the said pinch seal portion and the said rigid portion so as to stretch the plastic sealed lower end of the envelope relative to the remainder thereof with the support wire end caught in the seal so as to stretch and preload the said spring portion of the support wire.

References Cited UNITED STATES PATENTS 2,399,005 4/1946 Crawford 29-2515 2,695,442 11/1954 Klopping 29 25.16 2,802,131 8/1957 Meyer et al 2925.16 X 2,811,662 10/1957 Rishell 2925.16X 3,188,720 6/1965 Hushi 29 25.16 x 3,271,093 9/1966 Meier 29 25.15

PAUL M. COHEN, Primary Examiner US. 01. X.R. 

